1. Field of the Invention
The present invention relates to apparatus for producing an aerosol having a fan wheel located in a housing and driven by a motor whereby the fan wheel sucks air through a filter to remove bacteria and supplies this purified air to an atomising chamber which atomizes the fluid which it is desired to convert to an aerosol and thus supplies the aerosol.
An aerosol is a gas, especially air, which contains solid or fluid suspended substances in very fine dispersion. Aerosols of water and aqueous solutions with droplet sizes of 1 to 5 .mu.m (microns) are frequently used in medicine, where water-soluble medicaments can be added to the aqueous solutions to produce the aerosol. The aerosols of water and aqueous solutions which are used in medicine serve amongst other things to raise the humidity of the air in operating theatres and intensive care units and to humidify the patients' respiratory tract. It is important here for the aerosols to be germ-free in order to avoid possible infection. Germ-free aerosols can, however, only be produced with apparatus which itself operates in a germ-free manner.
2. Description of the Prior Art
A known apparatus for producing an aerosol for medical purposes (German Offenlegungsschrift No. 2218709) has an atomising chamber to which a fluid is supplied and atomised by means of an oscillator. A blower driven by a motor sucks air in through a filter to remove bacteria and supplies this air to the atomising chamber via a connecting pipe. The air supplied to the atomising chamber mixes with the atomised fluid particles and is discharged as an aerosol from the atomising chamber by means of a hose.
The blower consists of a fan wheel which is located in a separate compartment of a housing which accommodates the other parts of the known apparatus. The fan wheel is rigidly connected via a shaft to a motor which is arranged in its own adjacent compartment of the housing. The fan wheel and the motor together with the wall separating the two adjacent chambers form a closed inseparable unit. In this known apparatus the fan wheel can only be removed from the housing together with the motor and the dividing wall.
It has been found that, despite regular cleaning and changing, the filter provided to remove bacteria which is located in the intake opening of the fan cannot prevent pathogenic agents from collecting in the fan wheel and the space surrounding it and passing through the atomising chamber into the aerosol where they represent a source of infection.
Attempts have been made to arrange a further filter to remove bacteria at the outlet end of the hose leading out of the atomising chamber in order to increase the bacteriological purity of the air which is supplied by the atomiser. However, a filter of this type at the outlet end of the hose dispensing the aerosols absorbs a proportion of the fluid droplets and thereby lowers the humidity content of the aerosol. Furthermore, the fluid droplets absorbed in this filter provide a favourable atmosphere for the pathogenic agents, especially if the aerosol is warmed. As a result the filter at the outlet end of the hose for dispensing the aerosol has to be cleaned or changed after relatively short intervals of time.